High-frequency furnace



Dec. 8, 1953 B LQK HIGH-FREQUENCY FURNACE Filed Dec. ll, 1951 Lourens Blo k wwf/7% Agen? further load circuit is connected. One of the terminals i2 of the coupling coil is normally grounded, but, as an alternative the ground point of the coupling coil li may be shifted in place by 180 or 99 with respect to the output terminals I2- The unit is preferably made so as to be displaceable through a distance equal to the length of the circuit coil 3, the length of the coupling coil being adapted to this length. In a high-frequency furnace an adaptation of load may thus be ensured in a range which is sufficiently great for all practical uses. The ends of the circuit 2, which is constructed as a unit, are secured through flexible connecting leads l'l and I8 to the further` stationary part of the oscillator circuit. The connecting lead i3 is coupled through a blocking capacitor with the anode of the tube I and the connecting lead il is coupled through a grid capacitor t with the control-grid of the tube l and through a coil i with a grounded leak resistor i. The junction of the circuit capacitors l'. and li' is connected as shown in Fig. 2, through a lead it to the ground plate 22 and is grounded by way of the wheels 23 and the grounded rails 24.

The tube l is arranged laterally with respect to the displaceable structural unit, thus providing the further advantage that the loops of the flexible connections are only slightly deformed, when the structural unit is displaced. A screening strip 21 (partly removed in the drawing) is inserted between the tube and the circuit unit in order to avoid unwanted coupling of the grid circuit of the tube with other circuit elements. Any tendency of the circuit-arrangement towards parasitic oscillation is thus strongly reduced. For the same reasons it desirable to provide a screening plate 23 between the grid circuit and the anode circuit of the tube.

In the practical construction of the high-frequency furnace described above use was made of copper screening plates at right angles to the field of the coils and arranged on either side of the coupling coil ii and the circuit coil 3; one plate (25) is shown in broken lines in the ligure, the other (26) forms part of the screening box 2|. These screening plates are provided in order to permit housing the high-frequency furnace in a sheet-iron cabinet without electrical interference.

In the high-frequency furnace according to the invention, the flexible connections I6 to I3 do not transmit the comparatively high circuit or load currents, in contradistinction to known constructions of high-frequency furnaces. In the practical construction of a iii kw. high-frequency furnace comprising two tubes 'IBW 6/6000 in parallel connection, operating as the output tube, the flexible connections transmit approximately 3 amp. with a circuit current of about 8O amp.

The use of the invention provides a construction of a high-frequency furnace, which is attractive from the electrical point of view, the ad- 4 vantages of this construction largely compensating for the slightly less simple structural arrangement, particularly with the use of highfrequency furnaces of high power.

What I claim is:

1. A high-frequency furnace including an output discharge tube having an output electrode and an oscillatory circuit coupled to said electrode and constituted by a coil and a capacitance, a carrier for supporting said coil and said capacitance as a structural unit, an output coil xedly mounted in said furnace for inductively coupling said oscillatory circuit to a load, and means movably mounting said unit in said furnace to effect displacement of said circuit coil relative to said coupling coil.

2. A furnace as set forth in claim 1 further includingrneans to force-cool said circuit coil.

3. A high-frequency furnace including an output discharge tube having an output electrode and an oscillatory circuit coupled to said elec-l trode and constituted by a coil and a capacitance, said circuit coil being Wound in the form of a cylinder, a carrier for supporting said coil and said capacitance as a structural unit, an output coil nxedly mounted in said furnace for inductively coupling said oscillatory circuit to a load, said output coil being constituted by a cylindricaliy bent ribbon and surrounding said circuit coil, and means movably mounting said unit in said furnace to effect axial displacement 0f said circuit coil relative to said coupling coil.

l. A furnace as set forth in claim 3 wherein said tube is laterally displaced from said structural unit.

5. A high-frequency furnace including an output discharge tube having an output electrode and an oscillatory circuit coupled to said electrode and constituted by a coil and a capacitance, said circuit coil being wound in the form of a cylinder, a rolling carrier for supporting said coil and said capacitance as a structural unit, an output coil flxedly mounted in said furnace for inductively coupling said oscillatory circuit to a load, said output coil being constituted by a cylindrically bent ribbon and surrounding said circuit coil, and means including rails for moving said rolling carrier in said furnace to effect axial displacement of said circuit coil relative to said coupling coil through a distance equal to the axial length of said circuit coil.

LOURENS BLOK.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date i,043,272 Stokes et al Nov. 5, 1912 1,753,182 Harnrnarlund Apr. 1, 1930 2,294,413 Marshall Sept. l, 1942 2,522,035 Gusdorf et al Sept. 12, 1950 2,551,756 Mittelmann May 8, 1951 

